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Groups > sci.electronics.equipment > #367 > unrolled thread
| Started by | "Commander Kinsey" <CFKinsey@military.org.jp> |
|---|---|
| First post | 2020-06-18 14:03 +0100 |
| Last post | 2020-06-24 20:03 +0000 |
| Articles | 20 on this page of 103 — 11 participants |
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Error of % + digits? "Commander Kinsey" <CFKinsey@military.org.jp> - 2020-06-18 14:03 +0100
Re: Error of % + digits? "Commander Kinsey" <CFKinsey@military.org.jp> - 2020-06-18 14:28 +0100
Re: Error of % + digits? Pimpom <nobody@nowhere.com> - 2020-06-18 20:08 +0530
Re: Error of % + digits? "Commander Kinsey" <CFKinsey@military.org.jp> - 2020-06-18 15:41 +0100
Re: Error of % + digits? Ralph Mowery <rmowery28146@earthlink.net> - 2020-06-18 18:16 -0400
Re: Error of % + digits? "Commander Kinsey" <CFKinsey@military.org.jp> - 2020-06-18 23:48 +0100
Re: Error of % + digits? Ralph Mowery <rmowery28146@earthlink.net> - 2020-06-18 19:38 -0400
Re: Error of % + digits? "Commander Kinsey" <CFKinsey@military.org.jp> - 2020-06-19 21:46 +0100
Re: Error of % + digits? Ralph Mowery <rmowery28146@earthlink.net> - 2020-06-19 18:55 -0400
Re: Error of % + digits? "Commander Kinsey" <CFKinsey@military.org.jp> - 2020-06-19 23:59 +0100
Re: Error of % + digits? Pimpom <nobody@nowhere.com> - 2020-06-20 12:09 +0530
Re: Error of % + digits? "Commander Kinsey" <CFKinsey@military.org.jp> - 2020-06-20 13:03 +0100
Re: Error of % + digits? Ralph Mowery <rmowery28146@earthlink.net> - 2020-06-20 11:24 -0400
Re: Error of % + digits? "Commander Kinsey" <CFKinsey@military.org.jp> - 2020-06-20 16:58 +0100
Re: Error of % + digits? Pimpom <nobody@nowhere.com> - 2020-06-20 23:28 +0530
Re: Error of % + digits? Ralph Mowery <rmowery28146@earthlink.net> - 2020-06-20 14:15 -0400
Re: Error of % + digits? Tom Gardner <spamjunk@blueyonder.co.uk> - 2020-06-20 23:54 +0100
Re: Error of % + digits? Cydrome Leader <presence@MUNGEpanix.com> - 2020-06-26 05:10 +0000
Re: Error of % + digits? Ralph Mowery <rmowery28146@earthlink.net> - 2020-06-26 11:27 -0400
Re: Error of % + digits? Cydrome Leader <presence@MUNGEpanix.com> - 2020-06-27 06:40 +0000
Re: Error of % + digits? Ralph Mowery <rmowery28146@earthlink.net> - 2020-06-27 09:55 -0400
Re: Error of % + digits? Cydrome Leader <presence@MUNGEpanix.com> - 2020-06-29 02:59 +0000
Re: Error of % + digits? Ralph Mowery <rmowery28146@earthlink.net> - 2020-06-29 10:54 -0400
Re: Error of % + digits? Cydrome Leader <presence@MUNGEpanix.com> - 2020-06-30 03:28 +0000
Re: Error of % + digits? Jeroen Belleman <jeroen@nospam.please> - 2020-06-20 20:18 +0200
Re: Error of % + digits? "Commander Kinsey" <CFKinsey@military.org.jp> - 2020-06-24 18:37 +0100
Re: Error of % + digits? Cydrome Leader <presence@MUNGEpanix.com> - 2020-06-26 04:54 +0000
Re: Error of % + digits? "Commander Kinsey" <CFKinsey@military.org.jp> - 2020-07-11 21:38 +0100
Re: Error of % + digits? Cydrome Leader <presence@MUNGEpanix.com> - 2020-07-13 03:21 +0000
Re: Error of % + digits? "Commander Kinsey" <CFKinsey@military.org.jp> - 2020-07-13 13:32 +0100
Re: Error of % + digits? Cydrome Leader <presence@MUNGEpanix.com> - 2020-06-26 04:23 +0000
Re: Error of % + digits? Pimpom <nobody@nowhere.com> - 2020-06-26 14:02 +0530
Re: Error of % + digits? Cydrome Leader <presence@MUNGEpanix.com> - 2020-06-27 06:56 +0000
Re: Error of % + digits? "Commander Kinsey" <CFKinsey@military.org.jp> - 2020-07-12 18:45 +0100
Re: Error of % + digits? Pimpom <nobody@nowhere.com> - 2020-07-12 23:31 +0530
Re: Error of % + digits? Tom Gardner <spamjunk@blueyonder.co.uk> - 2020-07-12 20:21 +0100
Re: Error of % + digits? Pimpom <nobody@nowhere.com> - 2020-07-13 10:23 +0530
Re: Error of % + digits? "Commander Kinsey" <CFKinsey@military.org.jp> - 2020-07-13 13:36 +0100
Re: Error of % + digits? Pimpom <nobody@nowhere.com> - 2020-07-13 20:57 +0530
Re: Error of % + digits? Jeroen Belleman <jeroen@nospam.please> - 2020-07-13 17:39 +0200
Re: Error of % + digits? Tom Gardner <spamjunk@blueyonder.co.uk> - 2020-07-13 21:04 +0100
Re: Error of % + digits? "Commander Kinsey" <CFKinsey@military.org.jp> - 2020-07-20 21:35 +0100
Re: Error of % + digits? "Commander Kinsey" <CFKinsey@military.org.jp> - 2020-07-20 21:36 +0100
Re: Error of % + digits? Pimpom <nobody@nowhere.com> - 2020-07-21 12:05 +0530
Re: Error of % + digits? "Commander Kinsey" <CFKinsey@military.org.jp> - 2020-07-31 23:53 +0100
Re: Error of % + digits? Pimpom <nobody@nowhere.com> - 2020-08-01 14:31 +0530
Re: Error of % + digits? "Commander Kinsey" <CFKinsey@military.org.jp> - 2020-07-13 13:35 +0100
Re: Error of % + digits? Cydrome Leader <presence@MUNGEpanix.com> - 2020-07-16 07:30 +0000
Re: Error of % + digits? "Commander Kinsey" <CFKinsey@military.org.jp> - 2020-07-17 00:19 +0100
Re: Error of % + digits? Cydrome Leader <presence@MUNGEpanix.com> - 2020-07-21 01:13 +0000
Re: Error of % + digits? "Commander Kinsey" <CFKinsey@military.org.jp> - 2020-08-04 22:27 +0100
Re: Error of % + digits? Cydrome Leader <presence@MUNGEpanix.com> - 2020-09-09 07:39 +0000
Re: Error of % + digits? Jasen Betts <jasen@xnet.co.nz> - 2020-07-17 12:15 +0000
Re: Error of % + digits? "Commander Kinsey" <CFKinsey@military.org.jp> - 2020-07-28 19:02 +0100
Re: Error of % + digits? "Commander Kinsey" <CFKinsey@military.org.jp> - 2020-07-13 13:38 +0100
Re: Error of % + digits? Rich <rich@example.invalid> - 2020-06-24 20:06 +0000
Re: Error of % + digits? "Commander Kinsey" <CFKinsey@military.org.jp> - 2020-06-30 00:41 +0100
Re: Error of % + digits? Cydrome Leader <presence@MUNGEpanix.com> - 2020-06-30 03:52 +0000
Re: Error of % + digits? Ralph Mowery <rmowery28146@earthlink.net> - 2020-06-30 11:09 -0400
Re: Error of % + digits? Cydrome Leader <presence@MUNGEpanix.com> - 2020-07-02 05:45 +0000
Re: Error of % + digits? Jasen Betts <jasen@xnet.co.nz> - 2020-07-02 07:03 +0000
Re: Error of % + digits? Ralph Mowery <rmowery28146@earthlink.net> - 2020-07-02 10:41 -0400
Re: Error of % + digits? RheillyPhoull <Rheilly@bigslong.com> - 2020-07-03 09:20 +0800
Re: Error of % + digits? "Commander Kinsey" <CFKinsey@military.org.jp> - 2020-07-16 20:09 +0100
Re: Separate amps jacks on multimeters Rich <rich@example.invalid> - 2020-07-17 14:02 +0000
Re: Separate amps jacks on multimeters "Commander Kinsey" <CFKinsey@military.org.jp> - 2020-07-17 19:16 +0100
Re: Separate amps jacks on multimeters Rich <rich@example.invalid> - 2020-07-17 20:26 +0000
Re: Separate amps jacks on multimeters "Commander Kinsey" <CFKinsey@military.org.jp> - 2020-07-17 21:44 +0100
Re: Separate amps jacks on multimeters Rich <rich@example.invalid> - 2020-07-17 22:37 +0000
Re: Separate amps jacks on multimeters "Commander Kinsey" <CFKinsey@military.org.jp> - 2020-07-18 00:11 +0100
Re: Separate amps jacks on multimeters Ralph Mowery <rmowery28146@earthlink.net> - 2020-07-17 18:07 -0400
Re: Separate amps jacks on multimeters "Commander Kinsey" <CFKinsey@military.org.jp> - 2020-07-17 23:31 +0100
Re: Separate amps jacks on multimeters Ralph Mowery <rmowery28146@earthlink.net> - 2020-07-17 19:10 -0400
Re: Separate amps jacks on multimeters "Commander Kinsey" <CFKinsey@military.org.jp> - 2020-07-18 00:18 +0100
Re: Separate amps jacks on multimeters Ralph Mowery <rmowery28146@earthlink.net> - 2020-07-17 19:30 -0400
Re: Separate amps jacks on multimeters "Commander Kinsey" <CFKinsey@military.org.jp> - 2020-07-28 22:16 +0100
Re: Separate amps jacks on multimeters Cydrome Leader <presence@MUNGEpanix.com> - 2020-07-22 04:24 +0000
Re: Separate amps jacks on multimeters Ralph Mowery <rmowery28146@earthlink.net> - 2020-07-22 12:28 -0400
Re: Separate amps jacks on multimeters Ralph Mowery <rmowery28146@earthlink.net> - 2020-07-17 19:25 -0400
Re: Separate amps jacks on multimeters Cydrome Leader <presence@MUNGEpanix.com> - 2020-07-22 04:20 +0000
Re: Separate amps jacks on multimeters Ralph Mowery <rmowery28146@earthlink.net> - 2020-07-22 12:23 -0400
Re: Error of % + digits? Jasen Betts <jasen@xnet.co.nz> - 2020-07-03 13:10 +0000
Re: Error of % + digits? Ralph Mowery <rmowery28146@earthlink.net> - 2020-07-03 10:14 -0400
Re: Error of % + digits? "Commander Kinsey" <CFKinsey@military.org.jp> - 2020-07-16 20:10 +0100
Re: Error of % + digits? Ralph Mowery <rmowery28146@earthlink.net> - 2020-07-16 16:03 -0400
Re: Error of % + digits? Michael Terrell <terrell.michael.a@gmail.com> - 2020-07-16 13:13 -0700
Re: Error of % + digits? "Commander Kinsey" <CFKinsey@military.org.jp> - 2020-07-17 00:02 +0100
Re: Error of % + digits? Ralph Mowery <rmowery28146@earthlink.net> - 2020-07-16 23:29 -0400
Re: Error of % + digits? "Commander Kinsey" <CFKinsey@military.org.jp> - 2020-07-24 22:09 +0100
Re: Error of % + digits? Rich <rich@example.invalid> - 2020-07-24 22:58 +0000
Re: Error of % + digits? "Commander Kinsey" <CFKinsey@military.org.jp> - 2020-07-25 00:31 +0100
Re: Error of % + digits? "Commander Kinsey" <CFKinsey@military.org.jp> - 2020-07-17 00:01 +0100
Re: Error of % + digits? "Commander Kinsey" <CFKinsey@military.org.jp> - 2020-07-16 18:51 +0100
Re: Error of % + digits? Cydrome Leader <presence@MUNGEpanix.com> - 2020-07-26 03:53 +0000
Re: Error of % + digits? "Commander Kinsey" <CFKinsey@military.org.jp> - 2020-07-16 18:45 +0100
Re: Error of % + digits? Ralph Mowery <rmowery28146@earthlink.net> - 2020-07-16 15:53 -0400
Re: Error of % + digits? "Commander Kinsey" <CFKinsey@military.org.jp> - 2020-07-16 18:46 +0100
Re: Error of % + digits? Michael Terrell <terrell.michael.a@gmail.com> - 2020-07-16 10:54 -0700
Re: Error of % + digits? "Commander Kinsey" <CFKinsey@military.org.jp> - 2020-07-17 00:15 +0100
Re: Error of % + digits? Cydrome Leader <presence@MUNGEpanix.com> - 2020-07-26 04:17 +0000
Re: Error of % + digits? Rich <rich@example.invalid> - 2020-06-30 07:59 +0000
Re: Error of % + digits? Dieter Michel <dmichel@prosound.de> - 2020-06-22 17:19 +0200
Re: Error of % + digits? Rich <rich@example.invalid> - 2020-06-24 20:03 +0000
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| From | "Commander Kinsey" <CFKinsey@military.org.jp> |
|---|---|
| Date | 2020-06-18 14:03 +0100 |
| Subject | Error of % + digits? |
| Message-ID | <op.0merwlb4wdg98l@glass> |
I just bought an amp clamp meter, and it states the error is "+/- 1.9% + 3 digits". What does the "3 digits" part mean?
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| From | "Commander Kinsey" <CFKinsey@military.org.jp> |
|---|---|
| Date | 2020-06-18 14:28 +0100 |
| Message-ID | <op.0mes08jlwdg98l@glass> |
| In reply to | #367 |
On Thu, 18 Jun 2020 14:03:42 +0100, Commander Kinsey <CFKinsey@military.org.jp> wrote: > I just bought an amp clamp meter, and it states the error is "+/- 1.9% + 3 digits". What does the "3 digits" part mean? Answering my own question, I found this page, it means aswell as the percentage error, the last digit (eg the 2 in 147.2V) can vary by 3.: https://www.baylor.edu/content/services/document.php/49697.pdf
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| From | Pimpom <nobody@nowhere.com> |
|---|---|
| Date | 2020-06-18 20:08 +0530 |
| Message-ID | <Y%KGG.15263$qj7.470@fx04.ams1> |
| In reply to | #367 |
On 6/18/2020 6:33 PM, Commander Kinsey wrote: > I just bought an amp clamp meter, and it states the error is "+/- 1.9% + 3 digits". What does the "3 digits" part mean? > If your meter should read, say 1.875 A, the correct reading could be anywhere from 1.872 to 1.878. This is a possible error in the display presented to you in the analog-digital display conversion process. The +/-1.9% possible error is about the measurement taken including - but not only - any error made by the sensor. To put it another way: If the actual current is 1.875 A, inaccuracies in the sensor and associated circuits may process it as somewhere between 1.875 A +/-1.9%. The analog-digital process may introduce a further error of +/- 3 counts in the least significant display digit. Therefore a current of 1.875 A may be displayed as anywhere from 1.836 to 1.913 A.
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| From | "Commander Kinsey" <CFKinsey@military.org.jp> |
|---|---|
| Date | 2020-06-18 15:41 +0100 |
| Message-ID | <op.0meweog5wdg98l@glass> |
| In reply to | #369 |
On Thu, 18 Jun 2020 15:38:46 +0100, Pimpom <nobody@nowhere.com> wrote: > On 6/18/2020 6:33 PM, Commander Kinsey wrote: >> I just bought an amp clamp meter, and it states the error is "+/- 1.9% + 3 digits". What does the "3 digits" part mean? >> > > If your meter should read, say 1.875 A, the correct reading could > be anywhere from 1.872 to 1.878. This is a possible error in the > display presented to you in the analog-digital display conversion > process. The +/-1.9% possible error is about the measurement > taken including - but not only - any error made by the sensor. > > To put it another way: If the actual current is 1.875 A, > inaccuracies in the sensor and associated circuits may process it > as somewhere between 1.875 A +/-1.9%. The analog-digital process > may introduce a further error of +/- 3 counts in the least > significant display digit. Therefore a current of 1.875 A may be > displayed as anywhere from 1.836 to 1.913 A. Thanks, I wonder why all my other meters only list a % error. Is it included within it somehow, or are they just lying, or do some meters not have this error?
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| From | Ralph Mowery <rmowery28146@earthlink.net> |
|---|---|
| Date | 2020-06-18 18:16 -0400 |
| Message-ID | <MPG.3955b1ca946d909a989f1c@news.east.earthlink.net> |
| In reply to | #370 |
In article <op.0meweog5wdg98l@glass>, CFKinsey@military.org.jp says... > > > If your meter should read, say 1.875 A, the correct reading could > > be anywhere from 1.872 to 1.878. This is a possible error in the > > display presented to you in the analog-digital display conversion > > process. The +/-1.9% possible error is about the measurement > > taken including - but not only - any error made by the sensor. > > > > To put it another way: If the actual current is 1.875 A, > > inaccuracies in the sensor and associated circuits may process it > > as somewhere between 1.875 A +/-1.9%. The analog-digital process > > may introduce a further error of +/- 3 counts in the least > > significant display digit. Therefore a current of 1.875 A may be > > displayed as anywhere from 1.836 to 1.913 A. > > Thanks, I wonder why all my other meters only list a % error. Is it included within it somehow, or are they just lying, or do some meters not have this error? > > Most that use a digital meter should know the last digit is not accurate because of a rounding error. Say it shows 1.5 volts. It could be 1.45 to 1.55 or so and still show 1.5. Some meters such as the one under discussion is less accurate and can be 3 numbers high or low on the last digit. That is why on digital meters you should try to use a range that shows as many digits as you can. -My several hundred dollar Fluke meter shows DC volts to be .05 % +- 1 digit.
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| From | "Commander Kinsey" <CFKinsey@military.org.jp> |
|---|---|
| Date | 2020-06-18 23:48 +0100 |
| Message-ID | <op.0mfizcwhwdg98l@glass> |
| In reply to | #371 |
On Thu, 18 Jun 2020 23:16:50 +0100, Ralph Mowery <rmowery28146@earthlink.net> wrote: > In article <op.0meweog5wdg98l@glass>, CFKinsey@military.org.jp says... >> >> > If your meter should read, say 1.875 A, the correct reading could >> > be anywhere from 1.872 to 1.878. This is a possible error in the >> > display presented to you in the analog-digital display conversion >> > process. The +/-1.9% possible error is about the measurement >> > taken including - but not only - any error made by the sensor. >> > >> > To put it another way: If the actual current is 1.875 A, >> > inaccuracies in the sensor and associated circuits may process it >> > as somewhere between 1.875 A +/-1.9%. The analog-digital process >> > may introduce a further error of +/- 3 counts in the least >> > significant display digit. Therefore a current of 1.875 A may be >> > displayed as anywhere from 1.836 to 1.913 A. >> >> Thanks, I wonder why all my other meters only list a % error. Is it included within it somehow, or are they just lying, or do some meters not have this error? > > Most that use a digital meter should know the last digit is not accurate > because of a rounding error. Say it shows 1.5 volts. It could be 1.45 > to 1.55 or so and still show 1.5. Some meters such as the one under > discussion is less accurate and can be 3 numbers high or low on the last > digit. That is why on digital meters you should try to use a range that > shows as many digits as you can. Yes, but I was surprised to see up to 7 digits out on this one, depending on the range. I think DC amps is 3 or 5 dependant on range, and AC amps is 5 or 7. > -My several hundred dollar Fluke meter shows DC volts to be .05 % +- 1 > digit. The meters I have are not several hundred dollars, so are you saying they're only +/- 1 digit? Is the error much higher on the one under discussion because it's a clamp meter?
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| From | Ralph Mowery <rmowery28146@earthlink.net> |
|---|---|
| Date | 2020-06-18 19:38 -0400 |
| Message-ID | <MPG.3955c4e87f5fc9af989f1d@news.east.earthlink.net> |
| In reply to | #372 |
In article <op.0mfizcwhwdg98l@glass>, CFKinsey@military.org.jp says... > > -My several hundred dollar Fluke meter shows DC volts to be .05 % +- 1 > > digit. > > The meters I have are not several hundred dollars, so are you saying they're only +/- 1 digit? Is the error much higher on the one under discussion because it's a clamp meter? > > The larger error is because of the price difference. It costs more to make a part that is .01 % than it does to make one that is 2 %. The .01% parts may just be the 2 % ones that are hand sorted to .01%. I am sure that the clamp part does play some part in how accurate the meter is.
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| From | "Commander Kinsey" <CFKinsey@military.org.jp> |
|---|---|
| Date | 2020-06-19 21:46 +0100 |
| Message-ID | <op.0mg7zmz6wdg98l@glass> |
| In reply to | #373 |
On Fri, 19 Jun 2020 00:38:29 +0100, Ralph Mowery <rmowery28146@earthlink.net> wrote: > In article <op.0mfizcwhwdg98l@glass>, CFKinsey@military.org.jp says... >> > -My several hundred dollar Fluke meter shows DC volts to be .05 % +- 1 >> > digit. >> >> The meters I have are not several hundred dollars, so are you saying they're only +/- 1 digit? Is the error much higher on the one under discussion because it's a clamp meter? >> >> > > The larger error is because of the price difference. It costs more to > make a part that is .01 % than it does to make one that is 2 %. The > .01% parts may just be the 2 % ones that are hand sorted to .01%. > > I am sure that the clamp part does play some part in how accurate the > meter is. But what I'm surprised at is a £5 multimeter (not clamp) not giving a digits error. Maybe precision on a simple voltmeter is cheap as chips nowadays?
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| From | Ralph Mowery <rmowery28146@earthlink.net> |
|---|---|
| Date | 2020-06-19 18:55 -0400 |
| Message-ID | <MPG.39570c63e3c99f33989f1f@news.east.earthlink.net> |
| In reply to | #374 |
In article <op.0mg7zmz6wdg98l@glass>, CFKinsey@military.org.jp says... > > But what I'm surprised at is a £5 multimeter (not clamp) not giving a digits error. Maybe precision on a simple voltmeter is cheap as chips nowadays? > > You have to be careful how you throw precision and accurecy around. A meter that shows 4 digits is more precice than one that shows only 3 digits, however the 4 digit one may only be 1% accurate and the 3 digit one may be .5% accurate. It is easy to get precision, but difficule to be accurate. Think of it as shooting a gun. Precision may be how close the bullets land to each other where ever they land on the target, but to be accurate the bullets have to land on the center of the target. Such as all the bullets could land very close to each other, but not even hit the target. As I mentioned, a good meter will not have a digits error outside the +- one digit due to rounding.
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| From | "Commander Kinsey" <CFKinsey@military.org.jp> |
|---|---|
| Date | 2020-06-19 23:59 +0100 |
| Message-ID | <op.0mhd5c1iwdg98l@glass> |
| In reply to | #375 |
On Fri, 19 Jun 2020 23:55:42 +0100, Ralph Mowery <rmowery28146@earthlink.net> wrote: > In article <op.0mg7zmz6wdg98l@glass>, CFKinsey@military.org.jp says... >> >> But what I'm surprised at is a £5 multimeter (not clamp) not giving a digits error. Maybe precision on a simple voltmeter is cheap as chips nowadays? >> >> > > You have to be careful how you throw precision and accurecy around. > > A meter that shows 4 digits is more precice than one that shows only 3 > digits, however the 4 digit one may only be 1% accurate and the 3 digit > one may be .5% accurate. > > It is easy to get precision, but difficule to be accurate. Think of it > as shooting a gun. Precision may be how close the bullets land to each > other where ever they land on the target, but to be accurate the bullets > have to land on the center of the target. Such as all the bullets could > land very close to each other, but not even hit the target. > > As I mentioned, a good meter will not have a digits error outside the +- > one digit due to rounding. That didn't help. I interchange the two. I just want to know how close to the correct reading the readout is. Adding another digit doesn't improve anything if it's incorrect. And shooting all the bullets in one place doesn't help if they all miss.
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| From | Pimpom <nobody@nowhere.com> |
|---|---|
| Date | 2020-06-20 12:09 +0530 |
| Message-ID | <KaiHG.15698$qj7.139@fx04.ams1> |
| In reply to | #376 |
On 6/20/2020 4:29 AM, Commander Kinsey wrote: > On Fri, 19 Jun 2020 23:55:42 +0100, Ralph Mowery <rmowery28146@earthlink.net> wrote: > >> In article <op.0mg7zmz6wdg98l@glass>, CFKinsey@military.org.jp says... >>> >>> But what I'm surprised at is a £5 multimeter (not clamp) not giving a digits error. Maybe precision on a simple voltmeter is cheap as chips nowadays? >>> >>> >> >> You have to be careful how you throw precision and accurecy around. >> >> A meter that shows 4 digits is more precice than one that shows only 3 >> digits, however the 4 digit one may only be 1% accurate and the 3 digit >> one may be .5% accurate. >> >> It is easy to get precision, but difficule to be accurate. Think of it >> as shooting a gun. Precision may be how close the bullets land to each >> other where ever they land on the target, but to be accurate the bullets >> have to land on the center of the target. Such as all the bullets could >> land very close to each other, but not even hit the target. >> >> As I mentioned, a good meter will not have a digits error outside the +- >> one digit due to rounding. > > That didn't help. I interchange the two. I just want to know how close to the correct reading the readout is. Adding another digit doesn't improve anything if it's incorrect. And shooting all the bullets in one place doesn't help if they all miss. > Take pi as an example. It can be said that 3.14 is accurate as a three-digit value, but 3.1416 is more precise because it has a higher resolution. OTOH, deriving it from 22/7 or 3.1429 has the same 5-digit resolution and is just as precise as far as the number it represents is concerned but is less accurate. In this particular case, 3.1416 is both more precise and more accurate than 3.14 but that's not always the case with measurements. My mechanical slide caliper has a resolution of 0.001 inch. This means that it can display measurements with a precision of 1 mil, but that doesn't guarantee that a measurement taken with it will be accurate to 1 mil. I may not always press the jaws snugly enough and the scale may not be perfectly accurate.
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| From | "Commander Kinsey" <CFKinsey@military.org.jp> |
|---|---|
| Date | 2020-06-20 13:03 +0100 |
| Message-ID | <op.0miefkhkwdg98l@glass> |
| In reply to | #377 |
On Sat, 20 Jun 2020 07:39:37 +0100, Pimpom <nobody@nowhere.com> wrote: > On 6/20/2020 4:29 AM, Commander Kinsey wrote: >> On Fri, 19 Jun 2020 23:55:42 +0100, Ralph Mowery <rmowery28146@earthlink.net> wrote: >> >>> In article <op.0mg7zmz6wdg98l@glass>, CFKinsey@military.org.jp says... >>>> >>>> But what I'm surprised at is a £5 multimeter (not clamp) not giving a digits error. Maybe precision on a simple voltmeter is cheap as chips nowadays? >>>> >>>> >>> >>> You have to be careful how you throw precision and accurecy around. >>> >>> A meter that shows 4 digits is more precice than one that shows only 3 >>> digits, however the 4 digit one may only be 1% accurate and the 3 digit >>> one may be .5% accurate. >>> >>> It is easy to get precision, but difficule to be accurate. Think of it >>> as shooting a gun. Precision may be how close the bullets land to each >>> other where ever they land on the target, but to be accurate the bullets >>> have to land on the center of the target. Such as all the bullets could >>> land very close to each other, but not even hit the target. >>> >>> As I mentioned, a good meter will not have a digits error outside the +- >>> one digit due to rounding. >> >> That didn't help. I interchange the two. I just want to know how close to the correct reading the readout is. Adding another digit doesn't improve anything if it's incorrect. And shooting all the bullets in one place doesn't help if they all miss. >> > > Take pi as an example. It can be said that 3.14 is accurate as a > three-digit value, but 3.1416 is more precise because it has a > higher resolution. > > OTOH, deriving it from 22/7 or 3.1429 has the same 5-digit > resolution and is just as precise as far as the number it > represents is concerned but is less accurate. > > In this particular case, 3.1416 is both more precise and more > accurate than 3.14 but that's not always the case with measurements. > > My mechanical slide caliper has a resolution of 0.001 inch. This > means that it can display measurements with a precision of 1 mil, > but that doesn't guarantee that a measurement taken with it will > be accurate to 1 mil. I may not always press the jaws snugly > enough and the scale may not be perfectly accurate. I'd need to contract OCD to understand that. There's only one thing in question here, how close is the reading to the correct value. You can't split that into two. 3.1416 is better than 3.14, and that's it. All you can state with a reading is it's correct to within a certain percentage.
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| From | Ralph Mowery <rmowery28146@earthlink.net> |
|---|---|
| Date | 2020-06-20 11:24 -0400 |
| Message-ID | <MPG.3957f41475277903989f21@news.east.earthlink.net> |
| In reply to | #378 |
In article <op.0miefkhkwdg98l@glass>, CFKinsey@military.org.jp says... > > I'd need to contract OCD to understand that. There's only one thing in question here, how close is the reading to the correct value. You can't split that into two. 3.1416 is better than 3.14, and that's it. All you can state with a reading is it's correct to within a certain percentage. > > Try this. A doctor does a very complicated operation on your left arm like a joint replacement. It all goes very well. Very precise. However he should have done the operation on the right arm that was causing trouble. Not accurate. That is why a voltmeter can show 3 digits and be accurate to only the last digit being in question by one number either way, but a 5 digit volt meter can show many numbers, but if it is not calibrated corrctly the 2nd digit to the 5 th digit could be way off and the meter not accurate at all.
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| From | "Commander Kinsey" <CFKinsey@military.org.jp> |
|---|---|
| Date | 2020-06-20 16:58 +0100 |
| Message-ID | <op.0mipcac3wdg98l@glass> |
| In reply to | #379 |
On Sat, 20 Jun 2020 16:24:41 +0100, Ralph Mowery <rmowery28146@earthlink.net> wrote: > In article <op.0miefkhkwdg98l@glass>, CFKinsey@military.org.jp says... >> >> I'd need to contract OCD to understand that. There's only one thing in question here, how close is the reading to the correct value. You can't split that into two. 3.1416 is better than 3.14, and that's it. All you can state with a reading is it's correct to within a certain percentage. > > Try this. > > A doctor does a very complicated operation on your left arm like a joint > replacement. It all goes very well. Very precise. > > However he should have done the operation on the right arm that was > causing trouble. Not accurate. Nope, because the first one is 100% useless. I wouldn't call that precise at all, as he was out by half a metre. > That is why a voltmeter can show 3 digits and be accurate to only the > last digit being in question by one number either way, but a 5 digit > volt meter can show many numbers, but if it is not calibrated corrctly > the 2nd digit to the 5 th digit could be way off and the meter not > accurate at all. Showing those extra two numbers is pointless if they're wrong. All that matters is how many volts difference between the actual voltage and what is shown.
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| From | Pimpom <nobody@nowhere.com> |
|---|---|
| Date | 2020-06-20 23:28 +0530 |
| Message-ID | <U6sHG.61028$Nj4.43851@fx24.ams1> |
| In reply to | #380 |
On 6/20/2020 9:28 PM, Commander Kinsey wrote: > On Sat, 20 Jun 2020 16:24:41 +0100, Ralph Mowery <rmowery28146@earthlink.net> wrote: > >> In article <op.0miefkhkwdg98l@glass>, CFKinsey@military.org.jp says... >>> >>> I'd need to contract OCD to understand that. There's only one thing in question here, how close is the reading to the correct value. You can't split that into two. 3.1416 is better than 3.14, and that's it. All you can state with a reading is it's correct to within a certain percentage. >> >> Try this. >> >> A doctor does a very complicated operation on your left arm like a joint >> replacement. It all goes very well. Very precise. >> >> However he should have done the operation on the right arm that was >> causing trouble. Not accurate. > > Nope, because the first one is 100% useless. I wouldn't call that precise at all, as he was out by half a metre. > >> That is why a voltmeter can show 3 digits and be accurate to only the >> last digit being in question by one number either way, but a 5 digit >> volt meter can show many numbers, but if it is not calibrated corrctly >> the 2nd digit to the 5 th digit could be way off and the meter not >> accurate at all. > > Showing those extra two numbers is pointless if they're wrong. All that matters is how many volts difference between the actual voltage and what is shown. > You keep saying that it's only the accuracy that matters. That's true to some - and only some - extent. Now let's compare two different hypothetical meters, both 100% accurate. Let's say that meter A has 3.5 digits (max count 1999) and meter B is 4.5 digits (19999). Use them to measure a battery cell of exactly 1.612345V. Meter A will display 1.612V whereas meter B will show 1.6123V. Meter B allows you to evaluate the result to a higher degree of precision. Further suppose that both meters are not perfectly accurate and read 1% low. A will show 1.596V while B will read 1.5962V. B is still more precise in showing you what it thinks the voltage is. An order of magnitude more precise, in fact, even though both meters are off by -1%. That's how the term 'precision' is used in engineering. Perhaps what's confusing you is the fact that the term is more loosely applied in everyday language. As to the +/- 3 count (or 1 or whatever) possible error, it's an *uncertainty*, not a fixed inaccuracy, in digitizing an analog quantity. It will take too long to explain in detail here. Let me put it this way: If you measure the example voltage above multiple times with a meter with +/-3 count uncertainty, you may get a reading that varies from measurement to measurement by up to 6 points in the last digit. That's not a percentage inaccuracy.
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| From | Ralph Mowery <rmowery28146@earthlink.net> |
|---|---|
| Date | 2020-06-20 14:15 -0400 |
| Message-ID | <MPG.39581bfc1c591a73989f22@news.east.earthlink.net> |
| In reply to | #381 |
In article <U6sHG.61028$Nj4.43851@fx24.ams1>, nobody@nowhere.com says... > > You keep saying that it's only the accuracy that matters. That's > true to some - and only some - extent. > > > Sometimes it is precision. I worked at a company making polyester from raw materials. In a room was a panel with about 10 temperature gauges. At a certain time all gauges were marked and a sample of the material was sent to the lab. If it came back good, then the object was to keep all the gauges on the mark. It did not matter how far off the gauges were from the actual temperature. No mater how well we calibrated the guages there were several other factors that we had no control over. Such as the thermocouples they were connected to. The specifications were +- 3 deg C. on the thermocouples from the factory. If the temperature varied more than 1 deg C at 300 deg C it could mess up the material. So the object was precision and not accuracy.
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| From | Tom Gardner <spamjunk@blueyonder.co.uk> |
|---|---|
| Date | 2020-06-20 23:54 +0100 |
| Message-ID | <OswHG.241292$imF1.202211@fx15.am4> |
| In reply to | #382 |
On 20/06/20 19:15, Ralph Mowery wrote: > In article <U6sHG.61028$Nj4.43851@fx24.ams1>, nobody@nowhere.com says... >> >> You keep saying that it's only the accuracy that matters. That's >> true to some - and only some - extent. >> >> >> > > Sometimes it is precision. > > I worked at a company making polyester from raw materials. In a room > was a panel with about 10 temperature gauges. At a certain time all > gauges were marked and a sample of the material was sent to the lab. If > it came back good, then the object was to keep all the gauges on the > mark. It did not matter how far off the gauges were from the actual > temperature. No mater how well we calibrated the guages there were > several other factors that we had no control over. Such as the > thermocouples they were connected to. The specifications were +- 3 deg > C. on the thermocouples from the factory. If the temperature varied > more than 1 deg C at 300 deg C it could mess up the material. > > So the object was precision and not accuracy. I once worked for a company that made an instrument that measured cable attenuation to 0.001dB +- 0.1dB. The customers didn't care about the 0.1dB, since all they were interested in was the /stability/ of the 0.001dB and the ability to measure small changes. Why? Because the instrument measured the attenuation change as a function of temperature, and each temperature cycle test took 7 days. Yes, it was a /large/ drum of undersea cable.
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| From | Cydrome Leader <presence@MUNGEpanix.com> |
|---|---|
| Date | 2020-06-26 05:10 +0000 |
| Message-ID | <rd400g$egj$2@reader1.panix.com> |
| In reply to | #382 |
In sci.electronics.equipment Ralph Mowery <rmowery28146@earthlink.net> wrote: > In article <U6sHG.61028$Nj4.43851@fx24.ams1>, nobody@nowhere.com says... >> >> You keep saying that it's only the accuracy that matters. That's >> true to some - and only some - extent. >> >> >> > > Sometimes it is precision. > > I worked at a company making polyester from raw materials. In a room > was a panel with about 10 temperature gauges. At a certain time all > gauges were marked and a sample of the material was sent to the lab. If > it came back good, then the object was to keep all the gauges on the > mark. It did not matter how far off the gauges were from the actual > temperature. No mater how well we calibrated the guages there were > several other factors that we had no control over. Such as the > thermocouples they were connected to. The specifications were +- 3 deg > C. on the thermocouples from the factory. If the temperature varied > more than 1 deg C at 300 deg C it could mess up the material. > > So the object was precision and not accuracy. If the goal was keep the needle on their marks it does't have to mean anything was precise. Maybe your guages had no faces, or read mA instead of degrees, and bent needles. As long as your +/- 3 degree thermocouples and controllers did not jump up and down + and then -3 degrees all the time, you were good. It's like the zener diode or voltage standard that came up in this thread. Those have no precision. They may not even be accurate. They might be consistent though. Accuracy and precision by themselves can be useless where time or multiple readings are needed.
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| From | Ralph Mowery <rmowery28146@earthlink.net> |
|---|---|
| Date | 2020-06-26 11:27 -0400 |
| Message-ID | <MPG.395fddc930e6e0d6989f36@news.east.earthlink.net> |
| In reply to | #391 |
In article <rd400g$egj$2@reader1.panix.com>, presence@MUNGEpanix.com says... > > > So the object was precision and not accuracy. > > If the goal was keep the needle on their marks it does't have to mean > anything was precise. Maybe your guages had no faces, or read mA instead > of degrees, and bent needles. As long as your +/- 3 degree thermocouples > and controllers did not jump up and down + and then -3 degrees all the > time, you were good. > > One good example of what we had is this. In a vat of material is a test hole. In that hole is a rod about 3/8 inch in diameter and a foot long. At the end there are two thermocouples and two RTDs. The thermocouples wires go about 100 feet to a PLC (similar to a computer) card that converts the milivolts to digital that is then displayed on a compute screen. The RTDs go about 10 feet to a converter that converts the change in resistance to a 4 to 20 miliamp signal. That goes to a card on the PLC and then to the computer display. While the computer will display to 3 decimal places at 300 deg C from the lowest to the highest temperature shown on the display can be around 3 deg differnet and all 3 be within the limits of the equipmnet. At a certain time a sample is sent to the lab and one of the computer displays is set as a standard and the object of the PLC is to keep the actual temperature , whatever it actually is, to that 'standard'. Not too accurate as to temperature, but very precice. The operators only needed to keep that one computer display as close to that 'mark' as they can if for some reason the PLC messes up and they have to adjust the control manual.
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| From | Cydrome Leader <presence@MUNGEpanix.com> |
|---|---|
| Date | 2020-06-27 06:40 +0000 |
| Message-ID | <rd6pl5$42t$1@reader1.panix.com> |
| In reply to | #393 |
In sci.electronics.basics Ralph Mowery <rmowery28146@earthlink.net> wrote: > In article <rd400g$egj$2@reader1.panix.com>, presence@MUNGEpanix.com > says... >> >> > So the object was precision and not accuracy. >> >> If the goal was keep the needle on their marks it does't have to mean >> anything was precise. Maybe your guages had no faces, or read mA instead >> of degrees, and bent needles. As long as your +/- 3 degree thermocouples >> and controllers did not jump up and down + and then -3 degrees all the >> time, you were good. >> >> > > One good example of what we had is this. > > In a vat of material is a test hole. In that hole is a rod about 3/8 > inch in diameter and a foot long. At the end there are two > thermocouples and two RTDs. The thermocouples wires go about 100 feet > to a PLC (similar to a computer) card that converts the milivolts to > digital that is then displayed on a compute screen. The RTDs go about > 10 feet to a converter that converts the change in resistance to a 4 to > 20 miliamp signal. That goes to a card on the PLC and then to the > computer display. > > While the computer will display to 3 decimal places at 300 deg C from > the lowest to the highest temperature shown on the display can be around > 3 deg differnet and all 3 be within the limits of the equipmnet. > > At a certain time a sample is sent to the lab and one of the computer > displays is set as a standard and the object of the PLC is to keep the > actual temperature , whatever it actually is, to that 'standard'. Not > too accurate as to temperature, but very precice. The operators only > needed to keep that one computer display as close to that 'mark' as they > can if for some reason the PLC messes up and they have to adjust the > control manual. What's the control loop if the PLC dies? How do people control temperatures manually? Is there a foot pedal to stomp on to switch the heaters on and off? There's a couple machines I fuss with that use platinum junction RTDs and we have alarm limits set. If the machine drifts into an alarm state, outside of a warmup period that's pretty much the end of the day and everything stops until it can be fixed. The loops on these machines are tuned to maintain and hold a set point of less than 1 degree F. The displays are all wrong, show fake levels of precision, and read in C, but are wrong by several degrees, even if you do the math. We gave up trying to calibrate the displays against what the real temperature with the offset features when the probes were last changed. It just isn't worth the time. Those machines are not accurate, they're not precise (as measured with their own instrumentation), but they will absolutely hold a stable temperature if you can determine the set points yourself.
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